Pakistani air force jets bombed militant hideouts in the country's volatile northwest Thursday, officials said, after government efforts to negotiate a peace deal with the Pakistani Taliban broke down earlier this week.

ISLAMABAD, Pakistan — Ten heavily armed attackers stormed the international airport in Karachi, Pakistan’s largest city, late Sunday night, prompting an hours-long gun battle that left 19 dead, according to The Associated Press, before the assailants were killed, officials said.

Pakistani security forces declared the siege of Jinnah International Airport over about 4:30 a.m., five hours after the first sounds of gunfire and explosions sent travelers running for safety. Officials said that army soldiers killed the 10 attackers and that a large fire in one building was extinguished.

Just after dawn Monday, Pakistani forces conducted a precautionary sweep of the airport and declared that it would be cleared to resume flight operations by midday, said Asim Bajwa, spokesman for Pakistani security forces.

Pakistani news organizations initially reported 13 people were killed in the attack, including security personnel and at least one employee of Pakistan International Airlines, the state-run carrier. Passengers and airline staff were evacuated just after the attack began. The AP reported 19 victims had died.

The siege shocked a nation that has become accustomed to brazen terrorist assaults on its major cities. No group claimed responsibility, but suspicion immediately fell on the Pakistani Taliban, which has carried out coordinated attacks on military and civilian targets in recent months in what it has called retaliation for Pakistani strikes on its hide-outs in the country’s tribal areas.

Television news reports suggested that a parked plane was on fire, but officials said the blaze turned out to be in a nearby building. Bajwa said that “all vital assets (were) intact.”

Police officials said the attackers, who were wearing masks, airport security uniforms and large backpacks, raided the airport from three sides in a coordinated assault shortly before midnight, hurling hand grenades and firing heavy weapons. Authorities recovered rocket-propelled grenades and other weaponry.

Pakistani army troops and commandos surrounded the airport as civil aviation authorities issued an alert to all air facilities in the country. All flights into and out of Karachi were suspended.

Bajwa said that Pakistani forces cornered the attackers in two parts of the airport and “eliminated them.” Witnesses and social media accounts reported that firing could still be heard well into Monday morning.

“A heavy contingent of security officials are deputed to ensure security of passengers,” Munir Sheikh, a senior police official in Karachi, told the Los Angeles Times.

Eyewitnesses said the attackers were wearing suicide vests and carrying heavy ammunition.

“They entered the airport and started firing straight at the security officials. We hid just to save ourselves,” one young man told Pakistan’s Express News channel.

Another witness, an employee of a private company at the airport, told the channel that three of the attackers “looked like Uzbeks and Chinese. They were not local. They were wearing suicide jackets and had a lot of ammunition with them. They went toward the runway while firing.”

The channel did not identify the witnesses.

The gunmen entered the airport through the old terminal, which is generally used by charter flights and passengers embarking on the hajj, the Muslim pilgrimage to Mecca, Saudi Arabia. The airport, Pakistan’s busiest, is used by international carriers including Emirates, Cathay Pacific and Thai Airways, and several Pakistani and regional carriers.

Karachi, Pakistan’s commercial capital, has long been a target of militant attacks. A cease-fire between the government and the Pakistani Taliban, a federation of insurgent groups, expired in April after a failed bid to launch peace talks.

“Only organizations like al-Qaida and the Pakistani Taliban have the capability to carry out such attacks, and both have a presence in Karachi,” said a security official in Karachi who requested anonymity because of the sensitivity of the situation.

In a separate incident Sunday, suicide bombers attacked a hotel where Shiite Muslim pilgrims were staying in the volatile Baluchistan province, killing at least 23 people, according to provincial officials. No group claimed responsibility in that incident either, although attacks on minority Shiites in Baluchistan have often been carried out by sectarian militias that are distinct from the Pakistani Taliban.

Special correspondent Sahi reported from Islamabad and Times staff writer Bengali from Mumbai, India.